The present invention relates to a wire-electrical discharge machine.
Generally, wire-electrical discharge machining involves three to seven processing steps that include rough processing, intermediate processing, semi-finishing, and finishing, wherein the processing is performed while reducing the amount of energy. The purpose of this is to reduce the processing time by gradually reducing the surface roughness, as well as to increase the precision of the straightness of the processed surface. Furthermore, it is known that during wire-electrical discharge machining, due to wire vibration caused by discharge repulsion, electrostatic force or the like, the part of the wire facing the center part of a workpiece may become dented, or may swell into a so-called xe2x80x98drum shapexe2x80x99. Furthermore, the processing conditions are completely different between the first processing step (rough processing) and the subsequent processing steps (intermediate processing, semi-finishing, and finishing). In the first processing step, because processing is performed on a virgin workpiece, there is a danger that processing debris will not be adequately eliminated from the workpiece, and that the wire may break due to the presence of the debris.
FIG. 19 depicts a conventional wire-electrical discharge machine as disclosed in Japanese Patent Publication No. 7-16825, which includes input means 120 for inputting the plate thickness of a workpiece, the heights of nozzles and the like, processing parameter storage means 121 that stores the charging voltage, the ON period, the OFF period and the like, liquid pressure calculation means 122 that calculates the nozzle liquid pressure from the nozzle heights and other parameters, and processing parameter changing means 123 that changes the processing parameters based on the calculated nozzle liquid pressure, and seeks the nozzle liquid pressure, i.e., the processing liquid pressure, based on the nozzle heights, and changes the processing parameters based on the processing liquid pressure. In the first processing step, however, if the nozzles are sufficiently distanced from the workpiece, wire breakage is caused not by the liquid pressure during processing but by the wire length. It is therefore difficult to reliably prevent breakage of the wire using the method in which the processing parameters are calculated from the processing liquid pressure. In actual experiments, it has been determined that where the distance between the upper nozzle and the workpiece was 2 mm, (with a plate thickness of 20 mm and a wire having a diameter of 0.25 mm), the processing liquid pressure varies, but where the distance is longer than it, there is no change in processing liquid pressure. However, the problem arises that when the wire is long, it warps easily, and it is difficult to perform control when a short-circuit occurs, resulting in an increased likelihood of wire breakage. The present invention has been developed to solve the above-described problems, and an object thereof is to provide a wire-electrical discharge machine wherein the wire is not likely to break even where the nozzles are located at a distance from the workpiece. Furthermore, while the surface precision of the processed surface and processing accuracy are important in wire-electrical discharge machining, such processing accuracy is not taken into account in the conventional art.
The wire-electrical discharge machine according to a first aspect of the present invention includes processing parameter storage means that stores processing parameters, means that stores a relationship between a nozzle height and an amount of processing energy, processing energy determining means that determines the amount of processing energy during rough processing based on such relationship, and processing parameter changing means that changes the processing parameters based on the amount of processing energy. The workpiece is processed using the changed processing parameters. According to this construction, because the amount of processing energy is determined based on the wire nozzle height, the wire is not likely to break even where the nozzle is located at a far distance.
The wire-electrical discharge machine according to a second aspect of the present invention includes processing parameter storage means that stores standard processing parameters, means that stores a relationship between a nozzle height and an amount of liquid flow, means that determines the amount of liquid flow during rough processing based on such relationship, and liquid flow rate changing means that changes a liquid flow rate parameter among the processing parameters. The workpiece is processed using the changed processing parameters. According to this construction, because the processing liquid flow rate is determined in accordance with the nozzle height, the wire is not likely to break.
The wire-electrical discharge machine according to a third aspect of the present invention includes processing parameter storage means that stores standard processing parameters, means that stores a relationship between a nozzle height and an amount of wire tilt, tilt correction value determining means that determines the amount of wire tilt during processing based on such relationship, and tilt correction value changing means that changes a tilt correction value parameter among the processing parameters. The workpiece is processed using the changed processing parameters. According to this construction, the tilt caused by warping of the wire is corrected, thereby increasing surface precision and processing accuracy.
The wire-electrical discharge machine according to a fourth aspect of the present invention includes processing parameter storage means that stores standard processing parameters, means that stores a relationship between a nozzle height and an amount of wire shift, shift amount correction value determining means that determines the amount of wire shift during processing based on such relationship, and shift amount changing means that changes a wire shift amount parameter among the processing parameters. The workpiece is processed using the changed processing parameters. According to this construction, the amount of wire shift takes into account the degree of warping of the wire, thereby improving surface precision.
The wire-electrical discharge machine according to a fifth aspect of the present invention includes processing parameter storage means that stores standard processing parameters, nozzle distance detection means that detects a processing state in a first processing step and detects a nozzle distance from the detected processing state, and processing parameter determining means that determines the processing parameters for subsequent processing steps based on the detected nozzle distance. The workpiece is processed using the determined processing parameters. According to this construction, because the correct nozzle height can be automatically detected and correction can be performed in accordance with such nozzle height, surface precision can be improved.
In the wire-electrical discharge machine according to the fifth aspect of the present invention, the wire-electrical discharge machine according to a sixth aspect of the present invention detects the processing speed as the processing state. According to this construction, surface precision is improved.
In the wire-electrical discharge machine according to the fifth aspect of the present invention, the wire-electrical discharge machine according to a seventh aspect of the present invention further includes means for displaying a state of separation of a wire nozzle in a graphical fashion. According to this construction, errors during setting or inputting can be prevented.